News & Views
8 December 2017
The Challenges & Complexities of Storage Tank Cleaning

storage-tank-cleaning

Regular cleaning and maintenance of storage tanks is vital to ensure a clean and safe work environment, and to protect the integrity of the contents inside. Correct tank maintenance and cleaning will help you avoid:

Internal Moisture Build-up

Over time this can cause your tank to corrode from the inside out leading to tank damage and seepage. Moisture can also have a detrimental effect on the contents of your tank and cause multiple problems.

Sludge

Solids that have entered the tank eventually get broken down, settle on the bottom and become sludge. If not cleaned regularly, this can impact on the quality of contents in the tank and clog pipes. Sludge can also block filters and the passing of solids which in turn affects the operations of plants, vehicles, and boilers.

Microbial Contamination

These bacteria grow when moisture is present in the tank. The growing organisms thrive in these conditions, causing contamination, blockages and filter damage.

Tank Cleaning: Safety Hazards and Challenges

Cleaning the inside of an industrial tank carries multiple risks and safety concerns. Typical hazards encountered include:

Fire & Explosion

When a tank contains fuel or a flammable liquid, along with air which will undoubtedly be present during the cleaning process, you have 2 out of 3 elements necessary for a fire or explosion. The third element is a source of ignition which can come in many forms, including static electricity, electrical equipment, hot surfaces and exothermic reactions (iron sulphide).  Fuel and air are often unavoidable, so the only way to ensure you will not have an explosion is to completely remove the risk of ignition.

Chemical Hazards

Many toxic chemicals are present inside tanks and can be encountered during cleaning. Dangers arise when they come into contact with skin, they are inhaled or through accidental ingestion. Side effects can happen immediately or over time, and be short or long term depending on the chemical.

Oxygen Deficiency

Oxygen levels can drop well below the recommended concentration level of 20%. This needs to be tested and a breathing apparatus worn before entering. In a high risk tank, the oxygen level needs to be monitored throughout the cleaning process.

Physical Hazards

If an accurate risk assessment is not carried out by an experienced practitioner, issues can be encountered including objects falling, tripping, slippery surface, head injuries etc. These risks are generally worsened when the risk of fire is present as artificial lighting has to be kept to a minimum.

Microbiological

When water or sludge is present in the bottom of a tank allergic reactions and infections from contact or inhalation are a high risk.

Emissions

Emissions to both air and water can be dangerous depending on the toxicity of the chemical inside. Gas and flammable liquid released into the air and any emissions to water or the ground presents a significant environmental concern. Regulations must be strictly adhered to in this situation.

Cleaning and Maintaining Industrial Tanks

Over time all tanks will have a build-up of sludge, debris, contaminants and water. Regular cleaning is extremely important and all businesses with storage tanks should ensure they have an adequate maintenance plan. Tank cleaning and maintenance crews much be fully qualified and highly trained experts due to the inherent dangers posed by the task.

Methods used to clean the tank will vary depending on the unique circumstances of each tank and may include:

Non-Entry Tank Cleaning

The typical process involves removing all content from the tank and lowering the cleaning equipment in. This equipment is then used to pressure wash the tank from inside or to use expanding foam to ensure all chemical and contaminants are removed. Remote cameras can be used to monitor progress.

Manned Entry Tank Cleaning

In some circumstances manned entry to the tank is necessary. It is imperative that this cleaning method is carried out by experienced confined space entry crews to minimise risk. The crew will physically scrub the contaminants from the surface of the tank to ensure it is adequately cleaned.

Fuel Filtration/Fuel Polishing

Fuel is left in the tank and water and contaminants are filtered out. Fuel is circulated around the tank and remote video cameras and fibre optics are used to ensure accuracy.

Multipoint Pumping (Water)

Water build up is pumped at all available access points in a tank. Flexible suction tubes can be used here to remove water and contaminants across the entire bottom of a tank ensuring it is correctly emptied. The waste from the tank is then disposed of in a licensed facility.

It’s also important to note that in many cases Non Destructive Testing (NDT) is required for storage tanks for insurance purposes and to ensure regulatory compliance. This should be factored into an organisation’s tank maintenance program.

Enva provides a portfolio of safe and compliant Tank Cleaning and Decommissioning services. We are experts in confined space entry and developing customised tank maintenance programs for your exact tank requirements.

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